About Me

My mother was murdered by what I call corporate and political homicide i.e. FOR PROFIT! she died from a rare phenotype of CJD i.e. the Heidenhain Variant of Creutzfeldt Jakob Disease i.e. sporadic, simply meaning from unknown route and source. I have simply been trying to validate her death DOD 12/14/97 with the truth. There is a route, and there is a source. There are many here in the USA. WE must make CJD and all human TSE, of all age groups 'reportable' Nationally and Internationally, with a written CJD questionnaire asking real questions pertaining to route and source of this agent. Friendly fire has the potential to play a huge role in the continued transmission of this agent via the medical, dental, and surgical arena. We must not flounder any longer. ...TSS

Prions, infectious agents associated with transmissible spongiform
encephalopathy, are primarily composed of the misfolded and pathogenic form
(PrPSc) of the host-encoded prion protein. Because PrPSc retains infectivity
after undergoing routine sterilizing processes, the cause of bovine spongiform
encephalopathy (BSE) outbreaks are suspected to be feeding cattle meat and bone
meals (MBMs) contaminated with the prion. To assess the validity of prion
inactivation by heat treatment in yellow grease, which is produced in the
industrial manufacturing process of MBMs, we pooled, homogenized, and heat
treated the spinal cords of BSE-infected cows under various experimental
conditions.

Results

Prion inactivation was analyzed quantitatively in terms of the infectivity
and PrPSc of the treated samples. Following treatment at 140°C for 1 h,
infectivity was reduced to 1/35 of that of the untreated samples. Treatment at
180°C for 3 h was required to reduce infectivity. ***However, PrPSc was detected
in all heat-treated samples by using the protein misfolding cyclic amplification
(PMCA) technique, which amplifies PrPSc in vitro. Quantitative analysis of the
inactivation efficiency of BSE PrPSc was possible with the introduction of the
PMCA50, which is the dilution ratio of 10% homogenate needed to yield 50%
positivity for PrPSc in amplified samples.

Conclusions

Log PMCA50 exhibited a strong linear correlation with the transmission rate
in the bioassay; infectivity was no longer detected when the log PMCA50 of the
inoculated sample was reduced to 1.75. The quantitative PMCA assay may be useful
for safety evaluation for recycling and effective utilization of MBMs as an
organic resource.

IN fact, you should also know that the TSE Prion agent will survive in the
environment for years, if not decades.

you can bury it and it will not go away.

The TSE agent is capable of infected your water table i.e. Detection of
protease-resistant cervid prion protein in water from a CWD-endemic area.

it’s not your ordinary pathogen you can just cook it out and be done with.
that’s what’s so worrisome about Iatrogenic mode of transmission, a simple
autoclave will not kill this TSE prion agent.

I go from state to state trying to warn of the CWD and other TSE prion
disease in other species, I just made a promise to mom. back then, there was no
information.

so, I submit this to you all in good faith, and hope that you take the time
to read my research of the _sound_, peer review science, not the junk science
that goes with the politics $$$

right or left or teaparty or independent, you cannot escape the TSE prion
disease.

there is a lot of science here to digest, but better digesting this _sound_
science, instead of the junk political science you will hear from the shooting
pen industry.

I don’t care what you eat, or what party you are affiliated with, my
problem is, when you consume these TSE prions, and then go enter the medical,
surgical, dental, blood and tissue arena, then you risk exposing _me or MY_
family to the TSE prion disease via friendly fire, the pass it forward mode of
transmission mission, or what they call iatrogenic CJD. all iatrogenic CJD is,
is sporadic CJD, until the route and source of the TSE prion agent is proven.

I am NOT anti-hunter, I am or was a hunter (disabled with neck injury and
other medical problems), I am a meat eater.

I just don’t care for stupid, and sometimes you just can’t fix stupid, Lord
knows I have tried.

I do NOT advertise on these blogs, they are there for educational use. ...

New studies on the heat resistance of hamster-adapted scrapie agent:
Threshold survival after ashing at 600°C suggests an inorganic template of
replication

The infectious agents responsible for transmissible spongiform
encephalopathy (TSE) are notoriously resistant to most physical and chemical
methods used for inactivating pathogens, including heat. It has long been
recognized, for example, that boiling is ineffective and that higher
temperatures are most efficient when combined with steam under pressure (i.e.,
autoclaving). As a means of decontamination, dry heat is used only at the
extremely high temperatures achieved during incineration, usually in excess of
600°C. It has been assumed, without proof, that incineration totally inactivates
the agents of TSE, whether of human or animal origin.

Prion Infected Meat-and-Bone Meal Is Still Infectious after Biodiesel
Production

Histochemical analysis of hamster brains inoculated with the solid residue
showed typical spongiform degeneration and vacuolation. Re-inoculation of these
brains into a new cohort of hamsters led to onset of clinical scrapie symptoms
within 75 days, suggesting that the specific infectivity of the prion protein
was not changed during the biodiesel process. The biodiesel reaction cannot be
considered a viable prion decontamination method for MBM, although we observed
increased survival time of hamsters and reduced infectivity greater than 6 log
orders in the solid MBM residue. Furthermore, results from our study compare for
the first time prion detection by Western Blot versus an infectivity bioassay
for analysis of biodiesel reaction products. We could show that biochemical
analysis alone is insufficient for detection of prion infectivity after a
biodiesel process.

Detection of protease-resistant cervid prion protein in water from a
CWD-endemic area

The data presented here demonstrate that sPMCA can detect low levels of
PrPCWD in the environment, corroborate previous biological and experimental data
suggesting long term persistence of prions in the environment2,3 and imply that
PrPCWD accumulation over time may contribute to transmission of CWD in areas
where it has been endemic for decades. This work demonstrates the utility of
sPMCA to evaluate other environmental water sources for PrPCWD, including
smaller bodies of water such as vernal pools and wallows, where large numbers of
cervids congregate and into which prions from infected animals may be shed and
concentrated to infectious levels.

A Quantitative Assessment of the Amount of Prion Diverted to Category 1
Materials and Wastewater During Processing

Keywords:Abattoir;bovine spongiform encephalopathy;QRA;scrapie;TSE

In this article the development and parameterization of a quantitative
assessment is described that estimates the amount of TSE infectivity that is
present in a whole animal carcass (bovine spongiform encephalopathy [BSE] for
cattle and classical/atypical scrapie for sheep and lambs) and the amounts that
subsequently fall to the floor during processing at facilities that handle
specified risk material (SRM). BSE in cattle was found to contain the most oral
doses, with a mean of 9864 BO ID50s (310, 38840) in a whole carcass compared to
a mean of 1851 OO ID50s (600, 4070) and 614 OO ID50s (155, 1509) for a sheep
infected with classical and atypical scrapie, respectively. Lambs contained the
least infectivity with a mean of 251 OO ID50s (83, 548) for classical scrapie
and 1 OO ID50s (0.2, 2) for atypical scrapie. The highest amounts of infectivity
falling to the floor and entering the drains from slaughtering a whole carcass
at SRM facilities were found to be from cattle infected with BSE at rendering
and large incineration facilities with 7.4 BO ID50s (0.1, 29), intermediate
plants and small incinerators with a mean of 4.5 BO ID50s (0.1, 18), and
collection centers, 3.6 BO ID50s (0.1, 14). The lowest amounts entering drains
are from lambs infected with classical and atypical scrapie at intermediate
plants and atypical scrapie at collection centers with a mean of 3 × 10−7 OO
ID50s (2 × 10−8, 1 × 10−6) per carcass. The results of this model provide key
inputs for the model in the companion paper published here.

EUROPEAN COMMISSION HEALTH & CONSUMER PROTECTION DIRECTORATE-GENERAL
Directorate C - Scientific Opinions C1 - Follow-up and dissemination of
scientific opinions OPINION ON THE USE OF BURIAL FOR DEALING WITH ANIMAL
CARCASSES AND OTHER ANIMAL MATERIALS THAT MIGHT CONTAIN BSE/TSE ADOPTED BY THE
SCIENTIFIC STEERING COMMITTEE MEETING OF 16-17 JANUARY 2003 1 OPINION On 17 May
2002, the Scientific Steering Committee (SSC) was invited by Commission Services
to advice on the examples of conditions under which safe burial of potentially
TSE-infected (animal) materials can be achieved. The details of the SSC's
evaluation are provided in the attached report. The SSC concludes as follows:
(1) The term "burial" includes a diversity of disposal conditions. Although
burial is widely used for disposal of waste the degradation process essential
for BSE/TSE infectivity reduction is very difficult to control. The extent to
which such an infectivity reduction can occur as a consequence of burial is
poorly characterised. It would appear to be a slow process in various
circumstances. (2) A number of concerns have been identified including potential
for groundwater contamination, dispersal/transmission by birds/animals/insects,
accidental uncovering by man. (3) In the absence of any new data the SSC
confirms its previous opinion that animal material which could possibly be
contaminated with BSE/TSEs, burial poses a risk except under highly controlled
conditions (e.g., controlled landfill). The SSC reiterates the consideration
made in its opinion of 24-25 June 1999 on "Fallen Stock"1. The limited capacity
for destruction of animal wastes in certain countries or regions in the first
place justifies the installation of the required facilities; it should not be
used as a justification for unsafe disposal practices such as burial. However,
the SSC recognises that for certain situations or places or for certain diseases
(including animals killed and recycled or disposed of as a measure to control
notifiable diseases), the available rendering or incinerator or disposal
capacity within a region or country could be a limiting factor in the control of
a disease. Thus if hundreds or even millions of animals need to be rendered
after killing or if the transport of a material to a rendering or disposal plant
proved to be impractical, an appropriate case by case risk assessment2 should be
carried out before deciding upon the most appropriate way of disposal. In
principle, the risk is expected to be the lower for small incinerators3 as
compared to burial. As such decisions in practice may have to be taken at very
short notice, risk management scenarios according to various possible risks
should be prepared in advance to allow for a rapid decision when the need
arises.

1 Scientific Opinion on The risks of non conventional transmissible agents,
conventional infectious agents or other hazards such as toxic substances
entering the human food or animal feed chains via raw material from fallen stock
and dead animals (including also: ruminants, pigs, poultry, fish,
wild/exotic/zoo animals, fur animals, cats, laboratory animals and fish) or via
condemned materials. Adopted By the Scientific Steering Committee at its meeting
of 24-25 June 1999. (and re-edited at its meeting of 22-23 July 1999). 2 See
also the relevant sections and footnotes on risk assessment in the report
accompanying the SSC opinion of 24-25 June 1999. 3 See SSC opinion of 16-17
January 2003 on the use of small incinerators for BSE risk reduction. 2

THE USE OF BURIAL FOR DEALING WITH CARCASSES AND OTHER MATERIALS THAT MIGHT
CONTAIN BSE/TSE REPORT

1. MANDATE

On 17 May 2002, the Scientific Steering Committee (SSC) was invited by
Commission Services to advice on the examples of conditions under which safe
burial of potentially TSE-infected animal materials can be achieved. The SSC
appointed Prof.J.Bridges as rapporteur. His report was discussed and amended by
the TSE/BSE ad hoc Group at its meeting of 9 January 2003 and by the SSC at its
meeting of 16-17 January 2003.

2. GENERAL CONSIDERATIONS

"Burial" covers a range of disposal situations ranging from the practice of
burying animals on farms and other premises in a relatively shallow trench (with
or without treatment such as lining) to deep disposal to a lined and
professionally managed landfill site (SSC 2001). Buried organic material is
normally decomposed by microbial and chemical processes. However this is not a
process amenable to control measures. As noted by the SSC "Opinion on Fallen
Stock" (SSC 25th June 1999) there is little reliable information on the extent
and rate of infectivity reduction of BSE/TSEs following burial. An old paper by
Brown and Gajdusek 1991 assumed a reduction of 98% over 3 years. However it is
noted that the rate of degradation of materials following burial can vary very
considerably between sites. This is not surprising because the degradation
process is strongly influenced by factors such as water content of the site,
temperature inside the site, nature of adsorptive "material" present etc. The
previous SSC opinion noted that BSE/TSEs appear to be resistant to degradation
when stored at room temperature over several years. It also raised concerns that
mites could serve as a vector and/or reservoir for the infected scrapie
material. Burial sites may have a thriving animal population. Uncovering of risk
material that is not deeply buried is therefore possible. The SSC in its opinion
of 28th-29th June 2001 set out a framework for assessing the risk from different
waste disposal processes. These criteria may be applied to burial as
follows:

(1) Characterisation of the risk materials involved.

Unlike many other waste disposal options there are no technical or economic
factors that would limit the nature of the material that can be disposed of by
burial. Moreover in many cases the location of burial sites is uncertain. The
potential for transmission of BSE/TSEs for SRM that is buried near the surface
is also poorly characterised.3

(2) Risk reduction.

The extent to which the infectivity is reduced is likely to vary
substantially according to the nature of the site depth of burial whether
pre-treatment by burning or through the addition of lime is used etc. There
appears to be no scientific basis at present for the prediction of the rate of
loss of infectivity. In the absence of such data, as a worst case, it has to be
assumed that over a three-five year period the loss of infectivity may be
slight. In principle on a well-managed fully contained landfill the risks from
infective material can approach zero. However this requires rigorous management
over many years. This is difficult to guarantee.

(3) Degree to Which the Risks can be Contained

The principal concerns are:

* Prevention of access to the SRM by animals that could result in the
transmission (directly or indirectly) of the BSE/TSE.

* Penetration of prions into the leachate/groundwater. It is noted that on
some landfill sites leachate is sprayed into the air to facilitate oxidation of
some organic components. Such a practice could in principle lead to dispersal of
BSE/TSEs. It is also noted that it is not uncommon for landfill sites to be
re-engineered to increase their stability, gas and leachate flow and/or total
capacity. If this re-engineering involved an area where previous burial of
BSE/TSE contaminated material had taken place and additional risk could accrue.
The possibility of contaminated material being dug up in shallow and unmarked
burial sites on farms etc constitutes a considerably greater risk.

3. FURTHER INVESTIGATIONS

Research is needed on specific aspects of the behaviour of prion like
molecules in controlled landfills i.e.:

* Potential for adsorption to other material present in the waste that
might limit their mobility.

* Principal factors influencing rates of degradation.

* Effectiveness of encasement in cement in controlling/reducing the
risk.

4. CONCLUSION

In the absence of new evidence the opinion of the SSC "Opinion on Fallen
Stock" (SSC 25th June 1999) must be endorsed strongly that land burial of all
animals and material derived from them for which there is a possibility that
they could incorporate BSE/TSEs poses a significant risk. Only in exceptional
circumstances where there could be a considerable delay in implementing a safe
means of disposal should burial of such materials be considered. Guidelines
should be made available to aid on burial site selection.

ADOPTED BY THE SCIENTIFIC STEERING COMMITTEE AT ITS MEETING OF 16-17
JANUARY 2003

2 OPINION

On 17 May 2002, the Scientific Steering Committee (SSC) was invited by
Commission Services to advice on the examples of conditions under which safe
burning of potentially TSE-infected (animal) materials can be achieved. The
details of the SSC's evaluation are provided in the attached report. The SSC
concludes as follows:

(1) "Burning" covers a wide variety of combustion conditions. This opinion
is concerned with the process of open burning e.g. bonfires.

(2) There are serious concerns regarding the use of open burning for the
destruction of pathogen contaminated animal waste, particularly for waste which
may be contaminated with relatively heat stable pathogens. Issues include: the
potentially very high variability of the pathogen inactivation, the nature of
the gaseous and particulate emissions, and the risks from the residual
ash.

(3) The SSC recommends that open burning is only considered for pathogen
destruction under exceptional circumstances following a specific risk
assessment. In the case of animal waste possibly contaminated with BSE/TSE in
view of the uncertainty of the risk open burning should be considered a risk.
Suitable monitoring methods for TSE contamination of both air and ash are
needed. Protocols for safe burning in emergency situations need to be
established. The SSC reiterates the consideration made in its opinion of 24-25
June 1999 on "Fallen Stock"1. The limited capacity for destruction of animal
wastes in certain countries or regions in the first place justifies the
installation of the required facilities; it should not be used as a
justification for unsafe disposal practices such as burial. However, the SSC
recognises that for certain situations or places or for certain diseases
(including animals killed and recycled or disposed of as a measure to control
notifiable diseases), the available rendering or incinerator or disposal
capacity within a region or country could be a limiting factor in the control of
a disease. Thus if hundreds or even millions of animals need to be rendered
after killing or if the transport of a material to a rendering or disposal plant
proved to be impractical, an appropriate case by case risk assessment2 should be
carried out before deciding upon the most appropriate way of disposal. In
principle, the risk is expected to be the lower for small incinerators3 as
compared to open burning. As such decisions in practice may have to be taken at
very short notice, risk management scenarios according to various possible risks
should be prepared in advance to allow for a rapid decision when the need
arises. 1 Scientific Opinion on The risks of non conventional transmissible
agents, conventional infectious agents or other hazards such as toxic substances
entering the human food or animal feed chains via raw material from fallen stock
and dead animals (including also: ruminants, pigs, poultry, fish,
wild/exotic/zoo animals, fur animals, cats, laboratory animals and fish) or via
condemned materials. Adopted By the Scientific Steering Committee at its meeting
of 24-25 June 1999. (and re-edited at its meeting of 22-23 July 1999). 2 See
also the relevant sections and footnotes on risk assessment in the report
accompanying the SSC opinion of 24-25 June 1999. 3 See SSC opinion of 16-17
January 2003 on the use of small incinerators for BSE risk reduction. 3

OPEN BURNING OF POTENTIALLY TSE-INFECTED ANIMAL MATERIALS REPORT

1. MANDATE

On 17 May 2002, the Scientific Steering Committee (SSC) was invited by
Commission Services to advice on the examples of conditions under which safe
burning of potentially TSE-infected animal materials can be achieved. The SSC
appointed Prof.J.Bridges as rapporteur. His report was discussed and amended by
the TSE/BSE ad hoc Group at its meeting of 9 January 2003 and by the SSC at its
meeting of 16-17 January 2003.

2. GENERAL CONSIDERATIONS

Burning is a combustion process to which a range of control measures may be
applied to contain emissions and to ensure the completeness of the degradation
process for organic matter. Depending on the source (waste) material the burning
process may or may not require addition of other energy sources.
Incineration/pyrolysis are contained combustion processes are contained
combustion processes and therefore have the potential for a high level of
control. (However see opinion on small incinerators). At the other end of the
control spectrum is open burning; such as bonfires. Typically combustion of
animal waste requires the addition of a high calorific fuel in order to initiate
(and for some materials to sustain) the process. It is recognised that open
burning of animal waste is a very cheap and convenient method of disposal.
However uncontained burning has a number of problems in terms of the potential
risks involved:

(1) In the open burning situation a range of temperatures will be
encountered. It is difficult therefore to ensure complete combustion of the
animal waste. If the waste is contaminated with pathogens there will remain
considerable uncertainty as to the degree of their inactivation.

(2) Gaseous and particulate emissions to the atmosphere will occur and
consequently worker and public exposure is likely. There is very little data to
indicate whether or not some pathogens could be dispersed to air as a
consequence of open burning.

(3) The supporting/secondary fuel may be a source of contamination itself.
For example in the recent foot and mouth disease outbreak in the UK timbers were
used at some sites that were heavily contaminated with pentachlorophenol.

(4) The residual ash must be considered to be a risk source. Its safe
disposal needs to be assured (see opinion on small incinerators) to prevent
human and animal contact and protect from groundwater contamination. While
careful selection of burning sites can reduce the risks open burning should only
be considered in emergency situations. For each such emergency situation a
specific risk assessment should be conducted which must include the risk 4 from
the pathogen of immediate concern but also other pathogens that might be
present.

3. RISK ASSESSMENT OF OPEN BURNING FOR BSE

The SSC, at its meeting of 28th-29th June 2001, recommended "a framework
for the assessment of the risk from different options for the safe disposal or
use of meat and bone meal (MBM) and other products which might be contaminated
with TSEs and other materials. Applying the framework to the practice of open
burning, the following conclusions can be drawn:

3.1. Nature of the materials handled Potentially a wide variety of
materials can be used provided suitable secondary fuel is available. The burning
process is very simple in principle and difficult in practice to regulate
effectively.

3.2. Risk reduction due to open burning There is no reliable data to
indicate the extent of risk reduction that could be achieved by open burning. It
is reasonable however to assume that overall it will be rather less effective in
reducing the infectivity of BSE/TSE than wellconducted incineration. Moreover
the reproducibility of the risk reduction is likely to be very variable even at
a single location.

3.3. Airborne emissions and residue ash The composition of airborne
emissions and residue ash is rarely monitored. From a risk assessment viewpoint
particular attention needs to be given to the potential for the airborne
dispersal of relatively heat stable pathogens as a consequence of open burning.
In the absence of reliable data both airborne emissions and residual ash must be
considered to constitute a significant risk if animal waste that might be
contaminated with TSEs is being burnt.

4. FURTHER INVESTIGATION

Research is needed particularly on: * The potential for airborne dispersal
of relatively heat stable pathogens. * Methodologies to improve the efficacy of
the combustion process to ensure the inactivation of pathogen contaminated
animal waste.

5. CONCLUSION

Open burning potentially represents a significant risk where the animal
waste has the possibility of being contaminated with BSEs/TSEs. Suitable
monitoring methods for TSE contamination of both air and ash are needed.
Protocols for safe burning in emergency situations need to be established.

2 OPINION On 17 May 2002, the Scientific Steering Committee (SSC) was
invited by Commission Services to (i) evaluate a risk assessment1 prepared for
the UK's Spongiform Encephalopathy Advisory Committee (SEAC), on the potential
risk arising from the use of small incinerators to dispose of specified risk
materials and (ii) to advise on the safety with regard to TSE risks of the use
of such small incinerators.

The details of the SSC's evaluation are provided in the attached report.
The SSC concludes as follows:

(i) The SSC, at its meeting of 28th -29th June 2001, recommended "a
framework for the assessment of the risk from different options for the safe
disposal or use of meat and bone meal (MBM) and other products which might be
contaminated with TSEs and other materials." This framework comprised five
components:

(1) Identification and characterisation of the risk materials involved, the
possible means for their transmission and potential at risk groups.

(2) The risk reduction achieved by the particular process.

(3) The degree to which the risks can be contained under both normal and
emergency operating conditions. This inevitably includes consideration of the
effectiveness of control measures.

(5) The intended end-use of the products for example disposal, recycling
etc. The risk assessment prepared for SEAC focuses on the risks involved steps 1
and 2 in respect of BSE/TSEs only and is based on a visit to 10 incinerators out
of a total of 263 in the UK of which 60% had after burners. The risk assessment
is also using a number of assumptions and data that may be valid for certain
incinerator types under certain conditions, but are not necessarily applicable
either for all types of materials to be disposed of, or to the whole range of
types of small incinerators in use the EU and the UK.

(ii) Small incinerators are widely used to meet the needs of local
communities. These incinerators vary greatly in their design, nature of use and
performance characteristics and the quality of their management. As a
consequence of this variability there are many uncertainties in identifying
risks posed by small incinerators that are used to treat SRM materials and each
type should eventually receive its own assessment. Also, general operating and
control criteria should be established for

Potential risk sources arising from the incineration process include:
gaseous emissions and residual ash. Research is currently ongoing mimicking
incineration of TSE-infected brain tissue to assess the infectivity clearance
level under various scenarios2. However, there are no final reported
measurements that enable the risk to be assessed from either the emissions or
the ash from small incinerators. It has been argued that the protein content of
the ash is a reasonable surrogate measure of the degree of risk deduction caused
by the incineration process. This assumption is questionable in view of the
resistance to heat of prions as compared to other proteins. Protein measurements
in ash are however probably a useful general measure of the overall efficiency
and reproducibility of the incineration process. Results in the aforementioned
report1 indicate a large degree of variability in performance among the small
incinerators in the UK that have been evaluated. It is anticipated that small
incinerators, used by other Member States will also show a considerable
variation in performance. In evaluating the risk of small incinerators,
consideration should be given to the risk of potential contamination of the ash
and of the gaseous emissions. In the absence of generally accepted and enforced
performance standards for small incinerators handling SRMs each such facility
therefore needs to be the subject of a specific risk assessment. The SSC
considers that the standards set up by the new Waste Incinerator Directive
(2000/76/EC) and in its opinion of June 1999 on waste disposal should serve as
guidance. In the absence of reliable data on the possible residual infectivity
of the ash, it should be disposed of, i.e., in controlled landfills as described
in the SSC opinion of June 1999 on safe disposal of waste. The SSC finally
wishes to emphasise the need for suitable monitoring methods in order that risks
can be assessed readily for individual types of small incinerators. 2 P.Brown,
pers.comm., December 2002. Publication in progress.4

THE USE OF SMALL INCINERATORS FOR BSE RISK REDUCTION REPORT

1. MANDATE

On 17 May 2002, the Scientific Steering Committee (SSC) was invited by
Commission Services to (i) evaluate a risk assessment3 prepared for the UK's
Spongiform Encephalopathy Advisory Committee (SEAC), on the potential risk
arising from the use of small incinerators to dispose of specified risk
materials and (ii) to advise on the safety with regard to TSE risks of the use
of such small incinerators.

The SSC appointed Prof. J. Bridges as rapporteur. His report was discussed
and amended by the TSE/BSE ad hoc Group at its meeting of 9 January 2003 and by
the SSC at its meeting of 16-17 January 2003.

2. CURRENT LEGISLATIVE FRAMEWORK

Until 2000, small incinerators were exempt from the emission limits set by
the EC for MSW and hazardous waste incinerators with throughputs greater than 50
kg/hour. An "incineration plant" is defined by the new Incineration of Waste
Directive (2000/76/EC) as "any stationary or mobile technical equipment
dedicated to the thermal treatment of waste with or without recovery of the
combustion heat generated". This definition would appear to exclude open burning
of waste. The new Directive, which must be transposed into the legislation of
each Member State by December 2002, replaces a range of previous directives on
incineration. It applies to all new incinerator installations from December 28th
2002 and all existing installations from December 28th 2005. The principal aim
of the Directive is to prevent and/or limit negative environmental effects due
to emissions into air, soil, surface and ground water and the resulting risks to
human health from the incineration and co-incineration of waste. It covers many
aspects from a requirement for afterburners to airborne emission limits and
criteria for the composition of residual ash. Previous EC legislation has
exempted small incinerators (i.e. those operating at less than 50 kg per hour).
The Waste Incinerator Directive (WID) (2000) allows such small incinerators to
be exempt from licensing at the national level however they will still be
subjected to the same onerous requirements of the WID as larger
incinerators.

In the UK it is proposed that in future incinerators dealing with
non-hazardous waste but with a throughput of less than 1 tonne per hour will be
regulated by local authorities whereas those with a larger throughput will be
regulated by the national authority. It is possible that different regulatory
mechanisms may result in differences in the rigour with which the new standards
are enforced. The position on the disposal of animal waste is complicated.
Animal carcass incineration use not covered by the WID and therefore the
existing regulatory framework (90/66/EEC which covers animal and public health
requirements to ensure destruction of pathogens) will continue to be applied. A
new Animal By-Products Regulation

(ABPR) will apply in Member States during the first part of 2003. The
relationship to WID has been included in the ABPR. It is important that it does
not result in less strict standards being applied for animal carcass
incineration. In contrast to whole carcasses WID will apply to the burning of
meat and bone meal, tallow or other material (even if they burn animal carcasses
too). Additional specific directives will continue to apply to waste that could
be contaminated with BSE/TSEs. (96/449/EC)

3. CURRENT USE OF SMALL INCINERATORS TO DISPOSE OF ANIMAL WASTE Small
incinerators are used for a variety of purposes and in a range of locations
among Member States. Many are located alongside small abattoirs, knackers, hunt
kennels, or laboratories. Thus they meet the needs of relatively small
communities. Across Member States these small incinerators include a variety of
designs and operating conditions (as indicated above in principle they will
probably be required to meet specific standards for emissions and for the
composition of the residual ash by December 28th 2005). In the UK there are
indications (see DNV Report 2001) that a considerable quantity of SRM which
would have previously been sent for rendering is now being incinerated directly
in small incinerators. Thus evaluation of the risks from such incinerators is of
increasing importance.

4. RISK ASSESSMENT FOR SMALL INCINERATORS

The SSC, at its meeting of 28th -29th June 2001, recommended "a framework
for the assessment of the risk from different options for the safe disposal or
use of meat and bone meal (MBM) and other products which might be contaminated
with TSEs and other materials. This framework comprised five components:

(1) Identification and characterisation of the risk materials involved, the
possible means for their transmission and potential at risk groups.

(2) The risk reduction achieved by the particular process.

(3) The degree to which the risks can be contained under both normal and
emergency operating conditions. This inevitably includes consideration of the
effectiveness of control measures.

(5) The intended end-use of the products for example disposal, recycling
etc. Recently a report has been prepared by DNV consulting (2001) for the UK
Ministry of Agriculture, Fisheries and Food (now known as DEFRA) that assesses
the risks from small incinerators in the UK that receive SRMs. This report
focuses on the risks involved steps 1 and 2 in respect of BSE/TSEs only. 10
incinerators out of a total of 263 in the UK were visited of which 60% had after
burners.

(1) Nature of the materials handled.

The DNV report 2001 starts with the assumption that "the materials
incinerated at small abattoirs will be mainly SRM and bones from animals that
are fit for human consumption. It may also include material from animals failed
by meat inspectors. The likelihood of there being an animal 6 with significant
BSE infectivity is very small and certainly much less than for the fallen stock
handled by hunt kennels and knackers4. For this reason the study has
concentrated on the latter type of operation". The Report notes that "the
material handled by both knacker and hunt kennels is highly variable and
difficult to characterise". In terms of input the key factors to consider
are:

* The number of adult bovines processed and the proportion of these
carcasses that are likely to be infected.

* The extent of infectivity (in terms of human oral Infectious Units) that
may occur (average and worst case).

In the DNV (2001) risk assessment only the BSE risk from processing bovine
SRMs was considered. For quantitative risk assessment purposes the mean value of
the oral ID50 for cattle was taken as 0.1 gram. A range of values was taken to
cover uncertainty in the inter-species barrier from 104 to 1 (as recommended by
the SSC 2000). In order to assess the likelihood that a particular carcass could
be infected, UK and Swiss monitoring data was used. An incidence rate based on
Prionics test findings of between 0.013 and 0.0025 was calculated. The DNV
Report notes that prevalence rates are progressively reducing from these 1998/99
figures. Finally the report concludes that the SRM from an infected bovine could
contribute 700 Infectious Units.

(2) Risk reduction due to incineration

Once a carcass/SRM has been introduced into a small incinerator there are
two main sources for the potential release of BSE infectivity

(a) Airborne emissions (b) Residual ash

There is no direct data on the TSE levels that may occur in those two
media. The SSC however is aware of currently ongoing heat studies mimicking
various incineration conditions and scenarios and aiming at assessing the TSE
clearance efficacy of these processes (P.Brown, pers.comm., 16.01.03) on both
the residual ash and the trapped emission gases. In the absence of final data
from such experiments for individual (small) incinerator types, the DNV Report
(2001) assumes that measurement of the total protein content of ash is a
relevant surrogate for BSE/TSE material. Protein content is a useful indicator
of the general performance of an incinerator. However it is much more
problematic whether it is also a valid marker for possible BSE/TSE contamination
as it known that BSE/TSE are relatively heat resistant as compared to other
proteins. Failure to detect certain amino acids present in prions is encouraging
but the sensitivity limits for amino acids are relatively poor for reassurance
purposes. Equally important, the data provided in the DNV report shows moderate
split sample 4 It may be mentioned that this assumption may be valid for the UK
as a whole, but note necessarily for all other Member States. 7 variation but
often substantial inter sampling variation (up to 600 fold). This indicates a
wide span of performance standards among the small SRM incinerators in the UK
and most likely across the whole of the EU. Typically performance was
substantially poorer than is the case for larger incinerators. Unburned material
is not uncommonly noted in the ash from small incinerators. If the reduction in
protein content due to incineration is accepted as a valid indicator, typical
infectivity reduction can be calculated to be of the order of 1600 (DNV Report
2001). Incinerators are known to emit particulate matter from their stacks.
Larger incinerators have much higher stacks to facilitate disposal of emissions,
they also have gas cleaning equipment to minimise the emission of particulate
matter, metals and acidic gases. Small incinerators generally do not have any
gas cleaning equipment. It can be speculated (as in the DNV Report 2001) that
unburned materials (and therefore potentially infections is much less likely to
be emitted in the form of particulate matter than burnt material. Nonetheless
there is no data to support this assumption.

(3) Other considerations.

(a) Disposal of ash.

In the case of small incinerators ash is often dispersed of locally to a
trench, which is typically neither lined, nor is the residue buried deeply. In
contrast for larger incinerators in the UK ash is normally disposed of to a
contained landfill. The risk from disposal to a trench is difficult to gauge in
the absence of reliable data on the possible infectivity of the ash.

(b) Management factors.

Almost inevitably the level of expertise available for the management of
small incinerators is highly variable because few such facilities can afford to
employ specialists in incineration. This is also likely to be often the case for
the inspectors as well. While such considerations cannot formally be taken into
account in a risk assessment, they are not the less relevant factors that need
to be considered in assessing the risk from a particular plant.

(c) Benchmarking.

The DNV 2001 risk assessment relies greatly on the assumption that BSE/TSE
contaminated material is very unlikely to be processed. The Report seeks to
compare the risks from a small incinerator with that from large SRM incinerators
which the author had assessed previously (DNV, 1997). It identifies that the
risk is four-five -fold less from a typical small incinerator because the scale
of activities is much lower. However it is noted that the amount of experimental
data to back this conclusion is extremely limited and does not take into account
either risks from the residual ash or any consequences of a substantially lower
stack height limiting the dilution of the emitted particulate and gaseous
matter. 8

5. FURTHER INVESTIGATIONS

In view of the uncertainty regarding the risks due to BSE/TSE contamination
of the fly and bottom ash and airborne emissions it is recommended that further
research is conducted to identify the residual risks (along with attendant
uncertainties) from the burial of ash (without further treatment,) in
uncontained sites. It is essential that suitable monitoring methods are
developed.

Laboratory of Central Nervous System Studies, National Institute of
Neurological Disorders and Stroke, and Division of Environmental Protection,
Office of Research Facilities Development and Operations, National Institutes of
Health, United States Department of Health and Human Services, Bethesda,
Maryland 20892, National Homeland Security Research Center, Office of Research
and Development, United States Environmental Protection Agency, Research
Triangle Park, North Carolina 27711, and Institut Alfred Fessard, Centre
National de la Recherche Scientifique, 91198 Gif sur Yvette, France

We investigated the effectiveness of 15 min exposures to 600 and 1000 °C in
continuous flow normal and starvedair incineration-like conditions to inactivate
samples of pooled brain macerates from hamsters infected with the 263K strain of
hamster-adapted scrapie with an infectivity titer in excess of 109 mean lethal
doses (LD50) per g. Bioassays of the ash, outflow tubing residues, and vented
emissions from heating 1 g of tissue samples yielded a total of two
transmissions among 21 inoculated animals from the ash of a single specimen
burned in normal air at 600 °C. No other ash, residue, or emission from samples
heated at either 600 or 1000 °C, under either normal or starved-air conditions,
transmitted disease. We conclude that at temperatures approaching 1000 °C under
the air conditions and combustion times used in these experiments, contaminated
tissues can be completely inactivated, with no release of infectivity into the
environment from emissions. The extent to which this result can be realized in
actual incinerators and other combustion devices will depend on equipment design
and operating conditions during the heating process.

Introduction

Safe disposal of medical wastes, carcasses of cattle with bovine spongiform
encephalopathy (BSE), cervids with chronic wasting disease (CWD), sheep with
scrapie, and more generally, anyhumanor animal tissue infected or potentially
infected with one of the agents that cause transmissible spongiform
encephalopathy (TSE) continues to be an issue of concern. High temperature
incineration has been the method of choice for treatment of medical and
veterinary wastes by virtue of its proven ability to inactivate all types of
conventional pathogens, high throughput capacity, and significant volume
reduction. However, TSE agents are uniquely resistant to most physical and
chemical methods of disinfection, including dry heat (1-3).

In a previous series of experiments (4), we showed that transmission could
occur even after ashing infected tissue in a covered crucible at 600 °C: the ash
from one sample of fresh brain tissue heated for 15 min transmitted to five of
18 animals (another sample heated for 5 min did not transmit to any of the 15
animals), and one formalin-fixed sample heated for 5 min transmitted to one of
24 animals. As no transmissions occurred from any sample heated to 1000 °C, the
infectivity extinction point was somewhere between 600 and 1000 °C, most
probably very close to 600 °C, approaching the operating temperature of some
incineration units. Because of concerns about the reproducibility of these
unprecedented results, and about the possibility that some infectivity might be
entrained in stack gases vented during incineration, we designed an experimental
apparatus to produce conditions that reflect more closely actual incineration
conditions, in which gases flowed across a heated open crucible containing
contaminated tissue, oxidizing or pyrolyzing the tissue, and partially
entraining some of the ash; wealso performed infectivity bioassay measurements
of both ash and emissions. The 263K strain of hamster-adapted scrapie was chosen
because the concentration of infectivity in brain tissue of terminally ill
animals is as high or higher than in any other TSE, natural or experimental, and
thus allows the maximum measure of reduction, and because this strain shows
resistance to heat that is comparable to that of BSE and superior to other
tested TSE strains (refs 5-8 and personal communication from Dr. David Taylor,
Edinburgh, Scotland).

We here report that once again, despite the nearly total destruction of
over 109 LD50, and individual bioassay animal caging to avoid any possibility of
cross-contamination, an ashed sample of scrapie-infected tissue transmitted
disease after having been exposed to 600 °C for 15 min, and once again, we found
no survival after exposure to 1000 °C. We also show that no infectivity escaped
into air emissions from 15 min test burns at either 600 or 1000 °C.

Whatever the mechanism of this minimal level of survival in extreme
heatswhether a result of incomplete combustion, the existence of a mineralized
template for replication, or some other unimagined phenomenonsit may be
concluded that the exposure under carefully controlled laboratory conditions of
a small sample of contaminated tissue to 1000 °C, under either an oxidizing or
reducing atmosphere, will ensure complete sterilization of the ash and
emissions. Exposure at 600 °C allows a minimal level of infectivity to persist
in the ash but generates air emission products that are noninfective.

Experimental Procedures

Tissue Samples. Brains from 20 terminally ill hamsters infected with the
263K strain of hamster-adapted scrapie were pooled, homogenized, and distributed
into 1 g aliquots. The same procedure was used for a small pool of uninfected
control brains. Samples were frozen until the test burns were initiated.

Laboratory of Central Nervous System Studies, National Institute of
Neurological Disorders and Stroke, National Institutes of Health. ! Division of
Environmental Protection, National Institutes of Health.

Management Research Laboratory located at Research Triangle Park, NC.
Tissue samples were heated in a 2.54 cm (1 in.) diameter quartz reactor (Prism
Research Glass, Research Triangle Park, NC) placed inside a Lindberg furnace
(Blue M Model 542 32-V). Three separate, nearly identical quartz reactors were
used. One reactor was only used for the 1000 °C tests, and the other two were
alternated for the 600 °C tests. Gas flow through the experimental system was
controlled with a rotameter (Gilmont Instruments, a Barnant Company, Barrington,
IL).

A two-stage impinger was used to collect emissions from the gas stream
exiting the reactor: the first stage discharged the gas through deionized water
in a tube held in an ice bath; gas exhausted from the first impinger trap flowed
into a second trap suspended in dry ice within a polystyrene foam container. The
apparatus is shown schematically in Figure 1 and is photographed in Figure 2.
All components of the impinger system were made of quartz glass and connected
with Teflon couplings. Metal components were avoided because of their tendency
to bind amyloid protein (9). The entire apparatus was located in a fume hood.

The experimental matrix included testing of normal and infected tissues at
both 600 and 1000 °C. Experiments were performed under oxidative (combustion)
and reducing FIGURE 1. Schematic view of incineration simulation apparatus
showing, from left to right, the gas inlet, Lindberg furnace surrounding a
removable combustion chamber (quartz reactor tube), quartz exhaust tube,
emission impingers (ice water bath followed by dry ice bath), and exhaust
through filter into fume hood.

Before each test, the reactor was immersed for 30 min in a 1:1 aqueous
solution of freshly prepared sodium hypochlorite (Clorox bleach) and then
extensively rinsed with deionized water and allowed to dry. The clean, dry
reactor was then placed into the Lindberg furnace, and the furnace temperature
controls were adjusted to the desired setting based on calibrations that were
performed prior to the experiments. Each 1 g tissue sample was thawed and placed
into anewquartz crucible. Before beginning the experiments, a type-K
thermocouple (Omega, Model No. KQXL-18G-12) was used to measure the gas
temperature at the axial location of the reactor where the crucible would be
inserted. The temperature was allowed to equilibrate until no significant
temperature change occurred. The furnace temperature was then logged, and the
thermocouple was removed. After removal of the thermocouple, the impinger train
(Prism Research Glass, Research Triangle Park, NC) was installed onto the outlet
of the reactor, the inlet gas system was connected to the reactor, and the
temperature of the impinger train was logged. A bubble meter was used to perform
a leak check by setting the gas rotameter to the desired flow rate and checking
the impinger train outlet flow rate. After the leakage rate was determined for
each test and airflow was found to be within the acceptable range (50-70
mL/min), the tissue sample contained in the quartz crucible was placed into the
crucible holder and inserted into the reactor, and a clip was placed around the
joint between the reactor and the crucible holder. All samples were heated for
15 min.

Collection and Processing of Ash and Emission Samples. At the end of each
test burn, the clip holding the crucible holder to the reactor was removed, and
the crucible holder with crucible inside was removed and immediately cooled. The
crucible with its contained ash was then placed in a labeled sample vial. It was
noted that the reactor walls and crucible were coated with opaque, glasslike
surface deposits after the 1000 °C tests. When found in the reactor, these
deposits were dislodged using a stainless steel spatula, collected from the
reactor as thoroughly as possible, and placed in the labeled sample vial along
with the ash from each crucible. The collected ash and deposits were then
transferred to a Tenbroeck tissue grinder and homogenized in 1 mL of distilled
water.

Following each test burn, the impinger train was removed, labeled, and
sealed. The entire impinger train was placed at 4 °Cfor storage and later
transported to the National Institutes of Health in Bethesda, Maryland for
bioassay of the impinged emission materials that were recovered separately from
the glass tubing leading from the burner to the first impinger and from the
traps. Visible deposits from the tubing were assiduously scraped, rinsed into a
tissue grinder, and homogenized in 1mL of distilled water. Water from the first
trap was allowed to evaporate inside a laminar flow hood to a volume of
approximately 1 mL, which was transferred together with all associated tube
residues from both traps to a tissue grinder and homogenized. Each test burn
yielded three samples: (1) residue collected from the crucible and deposits from
the inside of the heated zone of the reactor (ash); (2) residue from the exhaust
zone of the reactor tube to the first impinger trap (exit tube residue); and (3)
commingled water and residues from the two impinger traps (air emission
samples).

Bioassays. The total volume of each sample was inoculated undiluted into
groups of healthy female weanling hamsters (0.05 mL per animal by the
intracerebral route; approximately 20 animals per sample). Twenty uninoculated
sentinel animals were randomly positioned among the inoculated bioassay animals,
all of which were individually caged, to avoid fighting and any possibility of
crosscontamination. Animals were observed for a period of 12 months for clinical
signs of scrapie, at which point the survivors were euthanized. The brains of
all animals, whether dying during the observation period, or surviving to its
conclusion, were examined for the presence of proteinaseresistant protein
(PrPres) by Western blot immunoassays.

The 12 month observation period was mandated by considerations of cost and
space associated with prolonged care of the largenumberof animals ( 450) needed
to conduct this study. The occurrence of rare transmissions after longer
incubation periods in rodents inoculated intracerebrally with low dose
infectious material has been documented (10, 11), but this possibility was
mitigated in our experiment by the examination of all brains for the presence of
PrPres, which is visible well before the onset of symptomatic disease (12, 13).

Western BlotImmunoassays. Approximately 0.1 gof brain tissue was extracted
per sample by the phosphotungstic acid method described by Safar et al. (14) and
blotted using the monoclonal anti-hamster PrP antibody 3F4 at a dilution of
1:2000. Samples giving a questionable positive result were reextracted using the
purification/concentration method of Xi et al. (15): all six such samples were
found to be clearly negative on retesting.

Results and Discussion

Bioassay results for each tested sample are summarized in Table 1. It is
important to note that the all material recovered from each test
burnsapproximately 1 mL volumes of resuspended ash, residues, or emissionsswas
inoculated to avoid any sampling error that can be significantwhendealing with
very low levels of infectivity.

Two unheated 263K brain tissue samples were assayed, yielding levels of
infectivity of 109.2 and 109.7 LD50/g of tissue macerate. Incubation periods in
the lowest dilution (10-1) groups were between 50 and 60 days; incubation
periods in the highest positive dilution groups (titration end point) ranged
from 120 to 180 days.

The residual ash from the 1 g sample of 263K brain macerate heated at 600
°C in normal air transmitted disease to two of 21 inoculated animals after
incubation periods of 261 and 303 days, and their brains were positive for
PrPres. The clinical signs and PrPres patterns in both hamsters were TABLE 1.
Bioassay Results for Combustion Products from Heated Infected Hamster Brain
Tissue Macerates and Controlsa test conditions bioassay specimen tissue gas °C
crucible exit tube traps

normal air ambient NA NA NA

normal air 600 0/20 NT NT

normal N2 603 0/21 0/18

normal air 1015 0/23 NT NT

normal N2 1000 0/20 0/18

infected air ambient NA NA NA

infected air 612 2/21 0/22 0/24

infected N2 598 0/20 0/19 0/26

infected air 996 0/15 0/26 0/23

infected N2 997 0/23 0/18 0/23

a For each test group, fractions represent number of PrPres-positive
animals over total number of inoculated animals. Residues from the exit tubes
and emissions from the impinger traps were combined for bioassays of the
uninfected control samples subjected to 600 and 1000 °C under N2. NA ) not
applicable; NT ) not tested.

No other heated samples were infectious, based on the absence of
symptomatic disease and brain PrPres, including reactor exit tube residues and
emission samples from tissues heated to 600 °C; ash, exit tube residues, and
emissions from tissues heated to 1000 °C; and normal brain tissue heated to 600
°C (bioassays were not done on normal tissue heated to 1000 °C). In particular,
no clinically healthy animal surviving to the observation end point was found to
have PrPres in the brain (i.e., no preclinical or subclinical infections were
detected 12 months after inoculation). All uninoculated sentinel animals also
remained asymptomatic and PrPresnegative. Comparison of Experimental and Actual
Incineration Conditions. The question as to whether medical waste incinerators
and other types of combustion units used for disposal of contaminated materials
provide the conditions necessary for inactivation of TSE cannot be completely
answered by laboratory experimentation. It is acknowledged that experiments such
as these cannot duplicate the dynamic operating conditions and complex rheology
of incinerators and the myriad of interactions with other waste constituents
that occur in a combustion environment. However, smallscale simulations can
provide valuable qualitative information regarding the behavior of materials in
a high temperature combustion environment under tightly controlled conditions.
With this limitation in mind, we offer the following comparisons of our
experimental conditions with those expected in actual incinerators and comment
on the implications of our data for potential environmental releases of
infectivity from combustion processes.

Types of Incinerators and Operating Temperatures. In the U.S., three types
of incinerators are typically used for disposal of medical wastes:
controlled-air two-stage modular systems, excess air batch systems, and rotary
kilns (16, 17). Of these, the controlled-air (also referred to as starved-air)
systems are the most widely used today (18). In these units, combustion of
wastes occurs in two stages. In the first stage, waste is fed into the primary
chamber, which is operated with less than the stoichiometric amount of air
required for combustion. Air enters from both above and below the burning bed of
waste, which is dried, volatilized, pyrolized, and partially combusted. In this
chamber, the air temperature above the waste is typically 760-980 °C. In the
second stage, air is added to the gases produced in the first chamber to
complete combustion, and the gas temperature is higher, typically 980-1095 °C.
The partial combustion of the waste in the first stage yields a gas with
sufficient heating value to operate the combustion process in the second stage
without the need for additional fuel. Gas temperatures in each chamber of
controlled-air incinerators are thus higher than the temperatures observed in
our experiments to achieve, respectively, near-total and total inactivation of
the agent. Excess air medical waste incinerators are typically small modular
units, usually designed with two chambers and provisions for manual loading of
waste into the primary chamber and removal of ash. Burners are ignited to bring
the secondary chamber to an operating temperature of 870- 980 °C. When this
temperature is reached, the burner in the primary chamber is ignited. The unit
is operated with levels of air that are approximately 100% higher than the
stoichiometric amount of air required for combustion.

The operating temperatures of modern medical waste incinerators, which
typically operate well above 600 °C, should reduce TSE infectivity
concentrations to levels at or very close to extinction. However, it should be
noted that these temperatures are usually measured in the gases above the bed of
burning waste, not in the bed itself. Themaximum temperatures achieved in the
bed may be as much as 100 °C lower than the gases, depending on the bed depth,
composition of the input material, and other factors. Accordingly, incinerators
used to dispose of TSEs should not be operated at lower temperatures. Indeed,
studies by theEPAhaveshown that incinerators operated at air temperatures of
about 600 °C may not even inactivate conventional pathogens that are much less
resistant to thermal inactivation than TSEcontaminated materials (35).

Large-volume, nonmedical waste streams that may contain TSE-contaminated
livestock and wildlife carcasses or meat and bone meal(MBM)have been disposed of
by various methods. In the U.K., all carcasses are incinerated in dual chamber
facilities with primary and secondary chamber temperatures of approximately 850
and 1000 °C, respectively. These incinerators typically operate at a carcass
input batch rate ranging between 100 and 1000 kg/h (average 450 kg/h), with a
solid-phase residence time of 1 h (personal communication, Dr. Stephen Wyllie,
Department for Environment, Food and Rural Affairs, U.K.). MBM may also be
incinerated, may be subjected to other thermal technologies including rotary
kilns, fluidized beds, and cement plants, or co-fired in power plants with fuels
such as coal, lignite, and other wastes (19). If these nonincineration systems
operate under conditions similar to incinerators, they may be expected to
provide a similar level of inactivation. Evaluations by the German Federal
Institute for Viral Illnesses in Animals and the Institute for Biological Safety
indicate that the incinerators used inGermanyfor disposal ofMBNcan achieve a
temperature of 600 °C for 15 min in the waste if specific operating conditions
are met (20, 21). Incinerators used in the U.S. for disposal of municipal waste
operate at temperatures above 1000 °C (22).

Concentration of the Infectious Agent. In these experiments, the waste load
consisted of pure brain tissue with an extremely high concentration of
infectivity (>109LD50/g). In actual incinerators, the concentration of
infectivity in the waste load will be much lower than that in our experiments
because the brain infectivity concentration in hamsters infected with the 263K
strain of scrapie is at least 2-3 logs higher than in livestock infected with
either BSE or scrapie (CWD brain has not been titered) and also because high
infectivity central nervous system tissues are diluted in the mix of peripheral
carcass (orMBM)tissues that contain little or no infectivity.

In medical waste incinerators, mixing of TSE tissues and contaminated items
with other materials also dilutes the concentration of the agent in the waste
load. Tissues usually comprise only a small percentage of the total volume of
most hospital waste streams; almost all of the mass of material that is
classified as medical waste is comprised of noninfectious materials such as
paper and plastic (23); and medical wastes are often burned together with
noninfectious, nonmedical waste.

Dilution of the infectious agent in a much larger volume of noninfectious
material is theoretically advantageous because it reduces the probability of the
agent being in localized areas of the incinerator, which may have less than
optimal conditions for inactivation. An example of such an area is the zone near
the incinerator walls, which may be cooler than the rest of the chamber.
Conversely, mixing TSE contaminated materials with other wastes could adversely
impact inactivation by insulating the agent and decreasing its total time of
exposure to inactivation temperatures. Combustion Gases. In some of these
experiments, pure nitrogen gas was used to simulate the combustion gas in the
primary chamber of a controlled-air incinerator. Oxygen in the small volume of
air that entered the reactor during the few seconds when the crucible holding
the tissue sample was inserted would have been rapidly purged from the system,
probably before the sample was dried out and heated

6158 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 38, NO. 22, 2004

to the target temperature. Thus, virtually all of the test burns using
nitrogen were carried out under anoxic conditions. This differs somewhat from
actual starved-air incineration conditions where limited amounts of air enter
the chamber throughout the combustion cycle, and partial oxidation of waste
constituents occurs. Volatilized organic and particulate materials from the
primary chamber enter the secondary chamber where excess air is added to
complete oxidization of these materials.

The ash from controlled-air incinerators has a relatively high carbon
content, typically from 3 to 6% and values as high as 30% are common (17). The
high carbon content is of concern because there is some evidence (24) that the
presence of carbon may protect TSE infectivity, and some of the residues
observed in the reactor exit tube and impinger traps in these experiments were
similar in color and form to carbon black.

Although the nitrogen used as a reactor carrier gas did not contain any
oxygen, as would be present in actual controlled-air incinerators, the results
yielded information relevant to inactivation mechanisms at higher temperatures.
No transmissions were detected in ash or emissions from infected issues in the
test burns performed in nitrogen, confirming that the presence of oxygen is not
required to inactivate the agent and that any carbon formed was not sufficiently
protective to prevent its inactivation. The lack of transmission from test burns
in anoxic conditions also suggests that denaturation or some inactivation
mechanism other than chemical oxidation may be operative at incineration
temperatures. These results may have potential application in selection of waste
processing technologies, particularly for high-volume waste streams such as MBM
and animal carcasses. High-temperature, anoxic waste pyrolysis systems that can
yield biofuels and other useful byproducts could be considered as alternatives
for incineration, which is usually a strictly destructive process.

SecondaryChamber.Another aspect of these experiments that differed from
actual incineration conditions was that the vented gases from the reactor tube,
which is functionally similar to the primary chamber of an incinerator, were
exhausted directly into a cold impinger train. In actual incinerators, the
vented emissions from the primary chamber typically enter a secondary chamber,
which is usually operated at a temperature higher than the primary chamber,
providing additional opportunity for the inactivation of any pathogens carried
in the gas phase. Depending on the system design, gases exiting the secondary
chamber may then be cooled and passed through scrubbers or other types of air
pollution control equipment before they are released to the environment. In our
experiments, no infectivity was detected in emission deposits collected directly
from the exhaust end of the reactor tube. This suggests that the agent would be
inactivated or retained in the ash in the first chamber of an incinerator and
that the potential for contamination of residues, wastewater, and other
effluents generated by gas cooling and air pollution control systems is minimal.

Conclusion

Any thermal treatment process whether incineration or alternative
technologys that ensures exposure of TSE wastes to temperatures of 1000 °C for
at least 15 min should result in sterile output products, as the minimum
temperature required to achieve sterility is probably only marginally above 600
°C. Treatment at 600 °C may thus produce an ash that is either sterile or
contains a level of residual infectivity well within regulatory requirements for
reductions of conventional pathogens in sterile products. In our experiments,
over one billion LD50 of scrapie infectivity were reduced to less than a single
LD50 (two transmissions among 21 inoculated animals) by a 15 min exposure to dry
heat at 600 °C. Although it may be objected that even this degree of reduction
does not achieve zero risk, it is approximately 10-fold greater than the most
stringent process validation guidelines issued by the FDA to ensure the safety
of biological products (up to 8 log virus removal) (25) or than the standard
used by the EPA for registration of sterilants (no growth of Bacillis subtilis
in 720 carriers each having at least 2 105 spore counts) (26). For TSE
inactivation conditions to be met, incinerators and other thermal treatment
systems must be properly selected and operated. In actual incinerators,
inactivation conditions can be adversely affected byanarray of operational
factors, such as overloading, cold start-ups and shut-downs, inadequate control
of air flow, insufficient or excessive turbulence, and loss of partially burned
material through grates. Under these failure mode conditions, inactivation may
be incomplete.'

Given a hypothetical potential for survival of trace amounts of TSE
infectivity in the combustion products of incinerators operated under suboptimal
conditions, the likelihood of disease transmission via environmental media is
minimized by several factors including the following: dilution; hydrophobic
properties of agents that would be expected to reduce their mobility in water
and soils; containment provided by ash landfill design and operations;
biological degradation; species barriers; and the inefficiency of likely routes
of exposure (27-32). It should also be noted that neither humans nor animals
appear to be susceptible to air-borne TSE infections, further diminishing any
potential risk from incinerator emissions.

Prior to this study, data on inactivation of TSE-infected tissues in
incinerator emissions were not available for risk assessment, and probabilistic
approaches were used to assess the risks of combustion processes, including the
burning of carcasses in open pyres. These approaches led to conclusions that the
risk of transmission to humans was extremely low (33, 34). Our study provides
actual data on inactivation under incineration conditions and offers further
reassurance that TSE materials can be safely disposed of via incineration.

well heck, this is just typical public relations fear factor control. do
you actually think they would spend the extra costs for fuel, for such extreme
heat, just to eliminate smell, when they spread manure all over your veg's. i
think not. what they really meant were any _TSE agents_.

b. Gas scrubbing to eliminate smoke -- though steam may be omitted;

c. Stacks to be fitted with grit arreaters;

snip...

1.2 Visual Imact

It is considered that the requirement for any carcase incinerator disign
would be to ensure that the operations relating to the reception, storage and
decepitation of diseased carcasses must not be publicly visible and that any
part of a carcase could not be removed or interfered with by animals or
birds.

*** The potential impact of prion diseases on human health was greatly
magnified by the recognition that interspecies transfer of BSE to humans by beef
ingestion resulted in vCJD. While changes in animal feed constituents and
slaughter practices appear to have curtailed vCJD, there is concern that CWD of
free-ranging deer and elk in the U.S. might also cross the species barrier.
Thus, consuming venison could be a source of human prion disease. Whether BSE
and CWD represent interspecies scrapie transfer or are newly arisen prion
diseases is unknown. Therefore, the possibility of transmission of prion disease
through other food animals cannot be ruled out. There is evidence that vCJD can
be transmitted through blood transfusion. There is likely a pool of unknown size
of asymptomatic individuals infected with vCJD, and there may be asymptomatic
individuals infected with the CWD equivalent. These circumstances represent a
potential threat to blood, blood products, and plasma supplies.

*** Spraker suggested an interesting explanation for the occurrence of CWD.
The deer pens at the Foot Hills Campus were built some 30-40 years ago by a Dr.
Bob Davis. At or abut that time, allegedly, some scrapie work was conducted at
this site. When deer were introduced to the pens they occupied ground that had
previously been occupied by sheep.

PO-039: A comparison of scrapie and chronic wasting disease in white-tailed
deer

snip...

After a natural route of exposure, 100% of WTD were susceptible to scrapie.
Deer developed clinical signs of wasting and mental depression and were
necropsied from 28 to 33 months PI. Tissues from these deer were positive for
PrPSc by IHC and WB. Similar to IC inoculated deer, samples from these deer
exhibited two different molecular profiles: samples from obex resembled CWD
whereas those from cerebrum were similar to the original scrapie inoculum. On
further examination by WB using a panel of antibodies, the tissues from deer
with scrapie exhibit properties differing from tissues either from sheep with
scrapie or WTD with CWD. Samples from WTD with CWD or sheep with scrapie are
strongly immunoreactive when probed with mAb P4, however, samples from WTD with
scrapie are only weakly immunoreactive. In contrast, when probed with mAb’s 6H4
or SAF 84, samples from sheep with scrapie and WTD with CWD are weakly
immunoreactive and samples from WTD with scrapie are strongly positive. This
work demonstrates that WTD are highly susceptible to sheep scrapie, but on first
passage, scrapie in WTD is differentiable from CWD.

After a natural route of exposure, 100% of white-tailed deer were
susceptible to scrapie. Deer developed clinical signs of wasting and mental
depression and were necropsied from 28 to 33 months PI. Tissues from these deer
were positive for scrapie by IHC and WB. Tissues with PrPSc immunoreactivity
included brain, tonsil, retropharyngeal and mesenteric lymph nodes, hemal node,
Peyer’s patches, and spleen. While two WB patterns have been detected in brain
regions of deer inoculated by the natural route, unlike the IC inoculated deer,
the pattern similar to the scrapie inoculum predominates.

In Objective 1, Assess cross-species transmissibility of transmissible
spongiform encephalopathies (TSEs) in livestock and wildlife, numerous
experiments assessing the susceptibility of various TSEs in different host
species were conducted. Most notable is deer inoculated with scrapie, which
exhibits similarities to chronic wasting disease (CWD) in deer suggestive of
sheep scrapie as an origin of CWD.

snip...

4.Accomplishments 1. Deer inoculated with domestic isolates of sheep
scrapie. Scrapie-affected deer exhibit 2 different patterns of disease
associated prion protein. In some regions of the brain the pattern is much like
that observed for scrapie, while in others it is more like chronic wasting
disease (CWD), the transmissible spongiform encephalopathy typically associated
with deer. This work conducted by ARS scientists at the National Animal Disease
Center, Ames, IA suggests that an interspecies transmission of sheep scrapie to
deer may have been the origin of CWD. This is important for husbandry practices
with both captive deer, elk and sheep for farmers and ranchers attempting to
keep their herds and flocks free of CWD and scrapie.

White-tailed Deer are Susceptible to Scrapie by Natural Route of Infection

snip...

This work demonstrates for the first time that white-tailed deer are
susceptible to sheep scrapie by potential natural routes of inoculation.
In-depth analysis of tissues will be done to determine similarities between
scrapie in deer after intracranial and oral/intranasal inoculation and chronic
wasting disease resulting from similar routes of inoculation.

"CWD has been transmitted to cattle after intracerebral inoculation,
although the infection rate was low (4 of 13 animals [Hamir et al. 2001]). This
finding raised concerns that CWD prions might be transmitted to cattle grazing
in contaminated pastures."

Please see ;

Within 26 months post inoculation, 12 inoculated animals had lost weight,
revealed abnormal clinical signs, and were euthanatized. Laboratory tests
revealed the presence of a unique pattern of the disease agent in tissues of
these animals. These findings demonstrate that when CWD is directly inoculated
into the brain of cattle, 86% of inoculated cattle develop clinical signs of the
disease.

Thank you for your correspondence regarding the review article Stanley
Prusiner and I recently wrote for Cold Spring Harbor Perspectives. Dr. Prusiner
asked that I reply to your message due to his busy schedule. We agree that the
transmission of CWD prions to beef livestock would be a troubling development
and assessing that risk is important. In our article, we cite a peer-reviewed
publication reporting confirmed cases of laboratory transmission based on
stringent criteria. The less stringent criteria for transmission described in
the abstract you refer to lead to the discrepancy between your numbers and ours
and thus the interpretation of the transmission rate. We stand by our assessment
of the literature--namely that the transmission rate of CWD to bovines appears
relatively low, but we recognize that even a low transmission rate could have
important implications for public health and we thank you for bringing attention
to this matter.

Warm Regards, David Colby

--

David Colby, PhDAssistant ProfessorDepartment of Chemical
EngineeringUniversity of Delaware

The identification and characterization of prion strains is increasingly
important for the diagnosis and biological definition of these infectious
pathogens. Although well-established in scrapie and, more recently, in BSE,
comparatively little is known about the possibility of prion strains in chronic
wasting disease (CWD), a disease affecting free ranging and captive cervids,
primarily in North America. We have identified prion protein variants in the
white-tailed deer population and demonstrated that Prnp genotype affects the
susceptibility/disease progression of white-tailed deer to CWD agent. The
existence of cervid prion protein variants raises the likelihood of distinct CWD
strains. Small rodent models are a useful means of identifying prion strains. We
intracerebrally inoculated hamsters with brain homogenates and phosphotungstate
concentrated preparations from CWD positive hunter-harvested (Wisconsin CWD
endemic area) and experimentally infected deer of known Prnp genotypes. These
transmission studies resulted in clinical presentation in primary passage of
concentrated CWD prions. Subclinical infection was established with the other
primary passages based on the detection of PrPCWD in the brains of hamsters and
the successful disease transmission upon second passage. Second and third
passage data, when compared to transmission studies using different CWD inocula
(Raymond et al., 2007) indicate that the CWD agent present in the Wisconsin
white-tailed deer population is different than the strain(s) present in elk,
mule-deer and white-tailed deer from the western United States endemic region.

Chronic wasting disease (CWD) is a widespread prion disease in cervids
(deer and elk) in North America where significant human exposure to CWD is
likely and zoonotic transmission of CWD is a concern. Current evidence indicates
a strong barrier for transmission of the classical CWD strain to humans with the
PrP-129MM genotype. A few recent reports suggest the presence of two or more CWD
strains. What remain unknown is whether individuals with the PrP-129VV/MV
genotypes are also resistant to the classical CWD strain and whether humans are
resistant to all natural or adapted cervid prion strains. Here we report that a
human prion strain that had adopted the cervid prion protein (PrP) sequence
through passage in cervidized transgenic mice efficiently infected transgenic
mice expressing human PrP, indicating that the species barrier from cervid to
humans is prion strain-dependent and humans can be vulnerable to novel cervid
prion strains. Preliminary results on CWD transmission in transgenic mice
expressing human PrP-129V will also be discussed.

Acknowledgement Supported by NINDS NS052319 and NIA AG14359.

PPo2-27:

Generation of a Novel form of Human PrPSc by Inter-species Transmission of
Cervid Prions

Prion diseases are infectious neurodegenerative disorders affecting humans
and animals that result from the conversion of normal prion protein (PrPC) into
the misfolded and infectious prion (PrPSc). Chronic wasting disease (CWD) of
cervids is a prion disorder of increasing prevalence within the United States
that affects a large population of wild and captive deer and elk. CWD is highly
contagious and its origin, mechanism of transmission and exact prevalence are
currently unclear. The risk of transmission of CWD to humans is unknown.
Defining that risk is of utmost importance, considering that people have been
infected by animal prions, resulting in new fatal diseases. To study the
possibility that human PrPC can be converted into the infectious form by CWD
PrPSc we performed experiments using the Protein Misfolding Cyclic Amplification
(PMCA) technique, which mimic in vitro the process of prion replication. Our
results show that cervid PrPSc can induce the pathological conversion of human
PrPC, but only after the CWD prion strain has been stabilized by successive
passages in vitro or in vivo. Interestingly, this newly generated human PrPSc
exhibits a distinct biochemical pattern that differs from any of the currently
known forms of human PrPSc, indicating that it corresponds to a novel human
prion strain. Our findings suggest that CWD prions have the capability to infect
humans, and that this ability depends on CWD strain adaptation, implying that
the risk for human health progressively increases with the spread of CWD among
cervids.

PPo2-7:

Biochemical and Biophysical Characterization of Different CWD
Isolates

Chronic wasting disease (CWD) is one of three naturally occurring forms of
prion disease. The other two are Creutzfeldt-Jakob disease in humans and scrapie
in sheep. CWD is contagious and affects captive as well as free ranging cervids.
As long as there is no definite answer of whether CWD can breach the species
barrier to humans precautionary measures especially for the protection of
consumers need to be considered. In principle, different strains of CWD may be
associated with different risks of transmission to humans. Sophisticated strain
differentiation as accomplished for other prion diseases has not yet been
established for CWD. However, several different findings indicate that there
exists more than one strain of CWD agent in cervids. We have analysed a set of
CWD isolates from white-tailed deer and could detect at least two biochemically
different forms of disease-associated prion protein PrPTSE. Limited proteolysis
with different concentrations of proteinase K and/or after exposure of PrPTSE to
different pH-values or concentrations of Guanidinium hydrochloride resulted in
distinct isolate-specific digestion patterns. Our CWD isolates were also
examined in protein misfolding cyclic amplification studies. This showed
different conversion activities for those isolates that had displayed
significantly different sensitivities to limited proteolysis by PK in the
biochemical experiments described above. We further applied Fourier transform
infrared spectroscopy in combination with atomic force microscopy. This
confirmed structural differences in the PrPTSE of at least two disinct CWD
isolates. The data presented here substantiate and expand previous reports on
the existence of different CWD strains.

The constant increase of chronic wasting disease (CWD) incidence in North
America raises a question about their zoonotic potential. A recent publication
showed their transmissibility to new-world monkeys, but no transmission to
old-world monkeys, which are phylogenetically closer to humans, has so far been
reported. Moreover, several studies have failed to transmit CWD to transgenic
mice overexpressing human PrP. Bovine spongiform encephalopathy (BSE) is the
only animal prion disease for which a zoonotic potential has been proven. We
described the transmission of the atypical BSE-L strain of BSE to cynomolgus
monkeys, suggesting a weak cattle-to-primate species barrier. We observed the
same phenomenon with a cattleadapted strain of TME (Transmissible Mink
Encephalopathy). Since cattle experimentally exposed to CWD strains have also
developed spongiform encephalopathies, we inoculated brain tissue from
CWD-infected cattle to three cynomolgus macaques as well as to transgenic mice
overexpressing bovine or human PrP. Since CWD prion strains are highly
lymphotropic, suggesting an adaptation of these agents after peripheral
exposure, a parallel set of four monkeys was inoculated with CWD-infected cervid
brains using the oral route. Nearly four years post-exposure, monkeys exposed to
CWD-related prion strains remain asymptomatic. In contrast, bovinized and
humanized transgenic mice showed signs of infection, suggesting that CWD-related
prion strains may be capable of crossing the cattle-to-primate species barrier.
Comparisons with transmission results and incubation periods obtained after
exposure to other cattle prion strains (c-BSE, BSE-L, BSE-H and cattle-adapted
TME) will also be presented, in order to evaluate the respective risks of each
strain.

Chronic wasting disease (CWD) is a contagious, rapidly spreading
transmissible spongiform encephalopathy (TSE) occurring in cervids in North
America. Despite efficient horizontal transmission of CWD among cervids natural
transmission of the disease to other species has not yet been observed. Here, we
report a direct biochemical demonstration of pathological prion protein PrPTSE
and of PrPTSE-associated seeding activity in skeletal muscles of CWD-infected
cervids. The presence of PrPTSE was detected by Western- and postfixed frozen
tissue blotting, while the seeding activity of PrPTSE was revealed by protein
misfolding cyclic amplification (PMCA). The concentration of PrPTSE in skeletal
muscles of CWD-infected WTD was estimated to be approximately 2000- to
10000-fold lower than in brain tissue. Tissue-blot-analyses revealed that PrPTSE
was located in muscle- associated nerve fascicles but not, in detectable
amounts, in myocytes. The presence and seeding activity of PrPTSE in skeletal
muscle from CWD-infected cervids suggests prevention of such tissue in the human
diet as a precautionary measure for food safety, pending on further
clarification of whether CWD may be transmissible to humans.

In the Archives of Neurology you quoted (the abstract of which was attached
to your email), we did not say CWD in humans will present like variant
CJD.

That assumption would be wrong. I encourage you to read the whole article
and call me if you have questions or need more clarification (phone:
404-639-3091). Also, we do not claim that "no-one has ever been infected with
prion disease from eating venison." Our conclusion stating that we found no
strong evidence of CWD transmission to humans in the article you quoted or in
any other forum is limited to the patients we investigated.

our results raise the possibility that CJD cases classified as VV1 may
include cases caused by iatrogenic transmission of sCJD-MM1 prions or food-borne
infection by type 1 prions from animals, e.g., chronic wasting disease prions in
cervid. In fact, two CJD-VV1 patients who hunted deer or consumed venison have
been reported (40, 41). The results of the present study emphasize the need for
traceback studies and careful re-examination of the biochemical properties of
sCJD-VV1 prions.

Weld County Bi-Products dba Fort Morgan Pet Foods 6/1/12 significant
deviations from requirements in FDA regulations that are intended to reduce the
risk of bovine spongiform encephalopathy (BSE) within the United States

World Organization for Animal Health (OIE) has upgraded the United States'
risk classification for mad cow disease to "negligible" from "controlled", and
risk further exposing the globe to the TSE prion mad cow type disease

U.S. gets top mad-cow rating from international group and risk further
exposing the globe to the TSE prion mad cow type disease